Method of transmitting and receiving data in network environment with wired and wireless networks bridged using relay portal

ABSTRACT

A method of transmitting and receiving data in a network environment with a wired network and a wireless network bridged using a relay portal is provided. The method includes choosing one of a plurality of portals sharing a wired network and a wireless network as a relay portal, and transmitting a data packet to the wired network by setting an identifier of the relay portal as a prioritized receiver of the data packet.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. patent application Ser.No. 11/435,901, filed on May 18, 2006, which is a Non-Provisional ofU.S. Provisional Patent Application No. 60/682,022, filed on May 18,2005, and claims the benefit of Korean Patent Application No.10-2005-0074413, filed on Aug. 12, 2005. The entire disclosures of theprior applications are hereby incorporated by reference in theirentirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the transmission and reception of data,and more particularly, to a method of transmitting and receiving data inan environment where a wired network and a wireless network areconnected to each other using a relay portal.

2. Description of the Related Art

Recently, there is an increasing demand for ultra high-speedcommunication networks due to widespread public use of the Internet anda rapid increase in the amount of available multimedia data. Since localarea networks (LANs) emerged in the late 1980s, the data transmissionrate over the Internet has drastically increased from about 1 Mbps toabout 100 Mbps. Thus, high-speed Ethernet transmission has gainedpopularity and wide spread use. Currently, intensive research into agigabit speed Ethernet is underway. An increasing interest in thewireless network connection and communication has triggered researchinto and development of wireless LANs (WLANs), greatly increasingavailability of WLANs to consumers. Although use of WLANs may reduceperformance in view of lower transmission rates and poorer stability ascompared to wired LANs, WLANs have various advantages, includingwireless networking capability, greater mobility and so on. Accordingly,WLAN markets have been gradually growing.

With the ever-growing demand for increasing the amount of datatransmitted over networks and with recent developments in wirelesstransmission technology, the IEEE 802.11a, 802.11b, 802.11g, 802.11n,and 802.11s standards have been suggested. These standards are improvedversions of the IEEE 802.11 standard, which is an initial WLAN standarddefining WLANs offering a transmission speed of 1-2 Mbps.Standardization among the IEEE 802.11a, 802.11b, 802.11g, 802.11n, and802.11s standards has already been completed or is underway.

However, there still exists a physical and economical limit inestablishing a network environment based solely on wireless networks.Therefore, various methods have been suggested for establishing anetwork environment by coupling wireless networks and wired networks,thereby expanding the entire network environment and reducing thedevelopment costs.

FIG. 1 is a diagram illustrating a conventional network topologyconfigured by wireless mesh networks. Referring to FIG. 1, mesh portals11 and 12 are relay devices which connect a wired network and a wirelessnetwork and both have a wireless interface and a wired interface. Mobilenodes (MNs) 15, 16, 17, and 18 only have a wireless interface foraccessing a wireless network. A mobile node can be connected to a meshportal via a wireless network and can be connected to a wired networkvia the mesh portal. Mesh portals and MNs may serve as access points(APs), in which case, they may directly connect MNs to each other via awireless network. Referring to FIG. 1, the MN 18 serves as an AP andthus configures its own basic service set (BSS).

Conventionally, in order to prevent a loop 14 from being generated inthe network topology illustrated in FIG. 1, the mesh portals 11 and 12have their own unique identifiers and broadcast them to a predeterminedwireless network. Then, MNs existing in the predetermined wirelessnetwork receive the unique identifiers of the mesh portals 11 and 12 andchoose one of the mesh portals 11 and 12. Thereafter, the MNs transmitand receive only broadcast packets transmitted by other MNs which choosethe same mesh portal as the one chosen by the MN doing the transmittingand receiving. Another way of preventing generation of a loop 14 is totransmit broadcast packets via only a single portal. In the case offorwarding unicast packets, MNs transmit the unicast packets to a wirednetwork via its chosen portal. Then, the chosen portal forwards onlypackets transmitted by MNs which exist in a wireless network and choosethe same.

FIG. 2 is a diagram illustrating a conventional network topology inwhich two separate wired networks are connected to a single wirelessnetwork.

In a network topology illustrated in FIG. 2, a wireless network isdivided into 3 groups 31, 32, and 33 which are managed by mesh portals21, 22, and 23, respectively. The wireless network operates normallywhen only one wired segment exists. However, when separate wiredsegments exist, the wireless network may not operate properly because,while choosing a mesh portal, MNs may block transmission of broadcastpackets by MNs belonging to another mesh portal or because MNs transmitunicast packets via only one mesh portal. For example, an MN 24 thatchooses the mesh portal 23 which is connected to a lower wired networkcannot transmit unicast packets to an upper wired network even though itcan still transmit data to the mesh portals 21 and 22 in a wirelessmanner.

Therefore, if a mesh portal is chosen as a connection to a wired networkin order to prevent a loop, it may be difficult to transmit data toanother wired network. However, if no mesh portal is chosen as aconnection to a wired network, a loop is likely to be generated.Therefore, it is necessary to develop methods and apparatuses fortransmitting data to a wired network while preventing a loop from beinggenerated.

SUMMARY OF EXEMPLARY EMBODIMENTS OF THE INVENTION

Exemplary embodiments of the present invention provide a method ofsetting a relay portal, which can prevent a loop from being generatedduring packet transmission.

Exemplary embodiments of the present invention also provide a method oftransmitting and receiving data in a wireless environment with a wirednetwork and a wireless network bridged using the relay portal.

These and other aspects of the present invention will be described in orbe apparent from the following description of the exemplary embodiments.

According to an aspect of the present invention, there is provided amethod of transmitting and receiving data in a network environment witha wired network and a wireless network bridged using a relay portal, themethod comprising choosing one of a plurality of portals sharing a wirednetwork and a wireless network as a relay portal, and transmitting adata packet to the wired network by setting an identifier of the relayportal as a prioritized receiver of the data packet.

According to another aspect of the present invention, there is provideda method of transmitting and receiving data in a network environmentwith a wired network and a wireless network bridged using a relayportal, the method comprising receiving a first packet for designating arelay portal, generating an update packet having the address of apredetermined device which transmits the first packet as a sourceaddress, transmitting the update packet using a broadcast method, andreceiving a second packet from the predetermined device and transmittingthe second packet to the wired network if a destination device which isto receive the second packet does not exist in the wireless network.

According to another aspect of the present invention, there is provideda method of transmitting and receiving data of a wireless deviceconnected to a wireless network, the method comprising receiving a datapacket which indicates the existence of a wireless network, analyzingthe received data packet and connecting to the wireless network, andregistering identifying information of the wireless device to a mainportal which has connected to the wireless network and a wired network.

According to still another aspect of the present invention, there isprovided a frame including an identifier of a receiving device which isto receive data, an identifier of a sending device which transmits thedata, and an identifier of one of a plurality of portals in a wirelessnetwork to which the sending device is connected.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects of exemplary embodiments of the presentinvention will become more apparent by describing in detail exemplaryembodiments thereof with reference to the attached drawings in which:

FIG. 1 is a diagram illustrating a conventional network topology inwhich a wireless network and a wired network are connected to eachother;

FIG. 2 is a diagram illustrating a conventional network topology inwhich two separate wired networks are connected to a single wirelessnetwork;

FIG. 3 is a diagram illustrating a network topology in which a wirednetwork is connected to 2 wireless networks, according to an exemplaryembodiment of the present invention;

FIG. 4 is a diagram illustrating a network topology in which twoseparate wired networks are coupled to each other by a wireless network,according to an exemplary embodiment of the present invention;

FIG. 5 is a diagram illustrating the format of a frame according to anexemplary embodiment of the present invention;

FIG. 6 is a flowchart illustrating the transmission of data by a mobilenode according to an exemplary embodiment of the present invention; and

FIG. 7 is a flowchart illustrating the transmission and reception ofdata using a mesh portal according to an exemplary embodiment of thepresent invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE INVENTION

Aspects of the present invention and methods of accomplishing the samemay be understood more readily by reference to the following detaileddescription of exemplary embodiments and the accompanying drawings. Thepresent invention may, however, be embodied in many different forms andshould not be construed as being limited to the exemplary embodimentsset forth herein. Rather, these exemplary embodiments are provided sothat this disclosure will be thorough and complete and will fully conveythe concept of the invention to those skilled in the art, and thepresent invention will only be defined by the appended claims. Likereference numerals refer to like elements throughout the specification.

The present invention is described hereinafter with reference toflowchart illustrations of methods according to exemplary embodiments ofthe invention. It will be understood that each block of the flowchartillustrations, and combinations of blocks in the flowchartillustrations, can be implemented by computer program instructions.These computer program instructions can be provided to a processor of ageneral purpose computer, special purpose computer, or otherprogrammable data processing apparatus to produce a machine, such thatthe instructions, which execute via the processor of the computer orother programmable data processing apparatus, create means forimplementing the functions specified in the flowchart block or blocks.

These computer program instructions may also be stored in a computerusable or computer-readable memory that can direct a computer or otherprogrammable data processing apparatus to function in a particularmanner, such that the instructions stored in the computer usable orcomputer-readable memory produce an article of manufacture includinginstruction means that implement the function specified in the flowchartblock or blocks.

The computer program instructions may also be loaded onto a computer orother programmable data processing apparatus to cause a series ofoperational steps to be performed on the computer or other programmableapparatus to produce a computer implemented process such that theinstructions that execute on the computer or other programmableapparatus provide steps for implementing the functions specified in theflowchart block or blocks.

And each block of the flowchart illustrations may represent a module,segment, or portion of code, which comprises one or more executableinstructions for implementing the specified logical function(s). Itshould also be noted that in some alternative implementations, thefunctions noted in the blocks may occur out of the order. For example,two blocks shown in succession may in fact be executed substantiallyconcurrently or the blocks may sometimes be executed in the reverseorder, depending upon the functionality involved.

The terms frequently used in this disclosure will now be defined.

Portal

A portal is a device connecting a wired network and a wireless networkand generally has two or more ports. In order to control such ports, aportal has a bridge function. A portal can be connected to anotherportal in a wired or wireless manner. When portals are connected in awired manner, they are physically connected by wired cables. The lengthof a wire connection between two portals may be extended by bridges.When portals are connected in a wireless manner, they are connected viaa wireless link. When portals are connected via a wireless link, theyare not necessarily connected directly to each other. In other words,portals can be indirectly connected via a wireless link through otherportals. Referring to FIG. 3, reference numerals 101, 103, and 104represent portals. The portals 103 and 104 are connected by wires.

Main Portal

One of a plurality of portals connected to one another in both a wiredmanner and a wireless manner is chosen as a main portal. For example, ofthe plurality of portals, the portal having the highest media accesscontrol (MAC) address may be chosen as a main portal.

Alternatively, of the plurality of portals, the portal which has beenconnected to a wired network the longest may be chosen as a main portal.

Referring to FIG. 3, of the portals 101, 103, and 104, the portals 103and 104 are connected to each other in both a wired manner and awireless manner. Thus, one of the portals 103 and 104 is chosen as amain portal. Since no portal is connected to the portal 101 in both awired manner and a wireless manner, the portal 101 becomes a mainportal.

Portals may notify MNs in a wireless network of their existence bytransmitting an advertisement frame throughout the entire wirelessnetwork. An advertisement frame transmitted by a portal may include theMAC address of the portal (or a unique identifier of the portal) andother necessary information such as information regarding a wirednetwork to which the portal is connected.

An MN receives an advertisement frame and the MN registers itsinformation with a main portal. The MN information registered with themain portal includes the MAC address of the MN. If the MN is an AP, itmay also register the MAC addresses of stations belonging to a BSS ofthe MN with the main portal. This registration process enables the mainportal to identify MNs included in a wireless network.

Relay Portal

An MN chooses one of a plurality of portals as a relay portal and usesthe chosen portal to transmit packets to a wired network. From theviewpoint of an MN, a main portal does not need to be the same as arelay portal. If an MN can designate one of a plurality of portals as arelay portal using an address field of a packet (e.g., a unicast packet,a multicast packet, or a broadcast packet) when transmitting the packetto a wired network, the portal designated as a relay portal mayrecognize that it has been chosen as a relay portal by the MN.Otherwise, the MN needs to notify the portal designated as a relayportal that it has been chosen as a relay portal.

When a portal recognizes for the first time that it has been chosen byan MN as a relay portal, the portal allows data received via a wirednetwork to which the portal is connected to be transmitted to the MNonly through the portal. For this, the portal chosen as a relay portalmay transmit to the MN a MAC frame (i.e., an IEEE 802.11f Layer 2 updateframe) whose source address is the address of the MN and whosedestination address is a broadcast address, thereby obtaining the effectof updating a filtering database of a bridge of portals other than theportal chosen as a relay portal. Therefore, when a packet which isdestined for the MN is transmitted from a wired network, thetransmission of the packet to the MN by portals other than the portalchosen as a relay portal is not allowed by bridges, i.e., only theportal chosen as a relay portal can forward the packet to the MN. If thepacket is transmitted from the wired network before one of a pluralityof portals is chosen as a relay portal, a main portal receives thepacket and transmits it to a wireless network.

The functions of a main portal and a relay portal will now be describedin detail with reference to FIG. 3. First, unicast transmission will nowbe described.

Referring to FIG. 3, the mesh portals 101 and 104 are main portals.

The transmission of a packet between MNs within a wireless network willfirst be described in detail with reference to the network environmentillustrated in FIG. 3. An MN 205 can directly transmit a packet to an MN206 via a wireless network because the MN 205 and the MN 206 can reacheach other via a wireless link.

The transmission of a packet from a wireless network to a wired networkwill now be described in detail with reference to the networkenvironment illustrated in FIG. 3. An MN in a wireless network choosesone of a plurality of mesh portals in the wireless network as a relayportal to transmit a packet to a predetermined MN outside the wirelessnetwork. Thereafter, the MN in the wireless network transmits a packetto the relay portal. Then, the relay portal transmits the packet to thepredetermined MN via the wired network. It is assumed that the MN 205chooses a mesh portal 103 as a relay portal to transmit a packet. Inthis case, the MN 205 transmits the packet first to the mesh portal 103.Then, the mesh portal 103 transmits the packet to a destination MN,i.e., a node 202, via a wired network.

According to the 802.11 address system, it is impossible to designate acertain mesh portal so that packets can be transmitted first to thecertain mesh portal. According to the current embodiment of the presentinvention, it is possible to designate a certain mesh portal so thatpackets can be transmitted first to this specific mesh portal, by usingan additional address field (Address 5). Address 5 can be used fordesignating a mesh portal so that unicast packets can be transmittedfirst to the mesh portal and for designating a mesh portal so that themesh portal can forward broadcast packets transmitted by an MN from awireless network to a wired network.

The transmission of a packet from a wired network to a wireless networkwill now be described in detail with reference to the networkenvironment illustrated in FIG. 3. If a packet transmitted from a wirednetwork is destined for an MN in a wireless network, the packet istransmitted to the MN in the wireless network via a relay portal chosenby the MN in the wireless network. The transmission of a packet from thenode 202 to the MN 205 will now be described in detail with reference tothe network environment illustrated in FIG. 3. Referring to FIG. 3, apacket transmitted by the node 202 is transmitted to the mesh portals103 and 104 via a wired network. Then, the mesh portal 103 which is arelay portal of the MN 205 forwards the packet to the MN 205. If thenode 202 transmits the packet via the wired network before the MN 205chooses one of the mesh portals 103 and 104 as its relay portal, themesh portal 103, as the main portal, forwards the packet to the MN 205.

The transmission of a broadcast packet in the network environmentillustrated in FIG. 3 will now be described in detail. When a broadcastoccurs within a wireless network, a broadcast packet is transmittedthroughout the entire wireless network. Of the plurality of portals inthe wireless network, the portal chosen as a relay portal of an MN whichhas transmitted the broadcast packet can forward the broadcast packet tothe wired network.

When a broadcast occurs in a wired network, only a main portal in thewired network can transmit a broadcast packet to the wireless network.Then, the broadcast packet is broadcast throughout the entire wirelessnetwork. Referring to FIG. 3, when a broadcast packet transmitted by theMN 205 in a wireless network is input to a wired port of a main portal,i.e., the mesh portal 104 of FIG. 3, via a relay portal, i.e., the meshportal 103 of FIG. 3, the mesh portal 104 compares information regardingMNs registered with the mesh portal 104, thereby preventing thebroadcast packet from being forwarded back to the wireless network.

FIG. 4 is a diagram illustrating a network topology in which twoseparate wired networks are coupled to each other by a wireless network,according to an exemplary embodiment of the present invention.

Wired networks 51 and 59 are not connected to each other by wires. Ifonly the wired network 51 is connected to the Internet, the wirednetwork 59 can be connected to the Internet through only the wirednetwork 51. Therefore, a wired network is needed to connect the wirednetworks 51 and 59.

As described above, one of a plurality of mesh portals connected to botha wired network and a wireless network is chosen as a main portal. Meshportals 113 and 114 are connected to both the wired network 51 and thewireless network, and mesh portals 117 and 118 are connected to both thewired network 59 and the wireless network. Therefore, a total of 2 ofthe mesh portals 113, 114, 117, and 118 are chosen as main portals.

An MN chooses one of the plurality of mesh portals connected to thewired network as a relay portal to transmit a packet to the wirednetwork. For example, an MN chooses one of the mesh portals 113 and 114,which are connected to the wired network 51, and one of the mesh portals117 and 118, which are connected to the wired network 59, as relayportals.

The transmission of a unicast packet in the network environmentillustrated in FIG. 4 will now be described in detail. The transmissionof a unicast packet within a wireless network is conducted in the samemanner as described above with reference to FIG. 3, and a detaileddescription thereof will be skipped.

The processes of transmitting a packet from a wireless network to awired network in a network environment illustrated in FIG. 4 are thesame as those described above with reference to FIG. 3 except that an MNchooses a relay portal for each of a plurality of wired networks andtransmits a packet to all the relay portals. Thereafter, once adestination MN recognizes that packets are transmitted via a particularrelay portal, the destination MN transmits the packets only to the relayportal. This is achieved by enabling all the portals to exchangeinformation regarding MNs which choose the portals or informationregarding MNs which are accessible through the portals. In other words,the portals store information regarding MNs which are reachable throughthe portals and provide the information to other portals so that theother portals can refer to the information when forwarding packets. Inaddition, portals provide MNs in a wireless network with informationregarding MNs which are reachable through the portals, thereby makingthe MNs in the wireless network transmit packets to a proper relayportal while preventing the packets from being forwarded using animproper relay portal.

For example, in a case where an MN 215 in the wireless network wishes totransmit a packet to an MN 212 outside the wireless network, the MN 215chooses one of the mesh portals 113 and 114, which are connected to thewired network 51 and share the wireless network, as a first relay portalof the MN 215 and chooses one of the mesh portals 117 and 118, which areconnected to the wired network 59 and share the wireless network, as asecond relay portal of the MN 215. If the MN 215 chooses the meshportals 113 and 118 as the first and second relay portals, respectively,of the MN 215, the MN 215 transmits a packet to the mesh portals 113 and118. Once the MN 215 recognizes that the MN 212 receives data via themesh portal 113, the MN 215 begins to transmit packets to the MN 212only via the mesh portal 113.

The transmission of a packet from a wired network to a wireless networkis transmitted in a similar manner as described above with reference toFIG. 3.

The transmission of a packet from a wired network to another wirednetwork in the network environment illustrated in FIG. 4, e.g., thetransmission of a packet to a destination MN, i.e., to a node 210, fromthe MN 212, will now be described in detail. In this case, a main portalreceives a packet from a wired network, determines whether a destinationMN for which the packet is destined exists in a wireless network, andtransmits the packet to a main portal of another wired network. Forexample, as illustrated in FIG. 4, a main portal, i.e., one of the meshportals 113 and 114, connected to the wired network 51 transmits apacket transmitted by the MN 212 to a main portal, i.e., one of the meshportals 117 and 118, connected to the wired network 59.

The transmission of a broadcast packet in the method illustrated in FIG.4 will now be described in detail. When a broadcast occurs inside awireless network, a broadcast packet is transmitted in the same manneras described above with reference to FIG. 3 except that, in the networkenvironment illustrated in FIG. 4, an MN designates a relay portal foreach of a plurality of wired networks and transmits a broadcast packetto each of the relay portals so that the relay portals can forward thebroadcast packet to the respective wired networks.

When a broadcast occurs inside a wired network, a broadcast packet istransmitted in the same manner as described above with reference to FIG.3. A broadcast packet wirelessly transmitted by a main portal iscontinuously transmitted by a main portal in a wired network.

FIG. 5 is a diagram illustrating the format of a frame according to anexemplary embodiment of the present invention. As described above,according to the 802.11 address system, since a prioritized transmissionof a packet is not possible using a certain portal, it is necessary todesignate an additional address field.

Therefore, according to the current exemplary embodiment of the presentinvention, an additional address field 503, i.e., Address 5, is used todesignate a portal to which packets must be transmitted with priority.In other words, for prioritized transmission of a packet to a relayportal, the address of the relay portal must be included in theadditional address field (Address 5) which is added for transmitting thepacket to the relay portal, and the packet must be transmitted first tothe relay portal at the address included in the additional address field(Address 5). Then, the relay portal transmits the packet to adestination MN. The additional address field (Address 5) may be used notonly for determining to which of a plurality of portals unicast packetsmust be transmitted first, but also for determining which of theplurality of portals is to forward broadcast packets from a wirelessnetwork to a wired network.

Referring to FIG. 5, a sequence number field 501 is used for preventingduplicate packets from being received, and a time-to-live (TTL) field502 is used for limiting the number of hops via which packets aretransmitted. A sequence number is a value added whenever a packet isgenerated and does not change while the packet is transmitted. An MNincreases a sequence number by 1 whenever it generates a packet. Whenreceiving a plurality of packets having the same sequence number, an MNwhich is supposed to forward the plurality of packets determines thatthe packets are duplicate packets and thus abandons the packets. The TTLfield 502 is used for allowing a packet to be transmitted through only alimited number of MNs. An MN reduces a TTL field value by 1 whenever itforwards a packet. When the TTL field value reaches 0, an MN abandonsthe corresponding packet.

In a case where a portal is not a destination MN but exists along a pathto the destination MN, it is possible to enable a packet to betransmitted first to the portal by using an encapsulation method insteadof using the aforementioned additional address field-based method. Inthe encapsulation method, an 802.11 header is additionally attached to aMAC protocol data unit (MPDU). The address of a portal to which a packetmust be transmitted first is set as a destination address of the 802.11header so that the packet can be transmitted first to the portal. Then,the portal removes the 802.11 header from the packet and transmits theresulting packet to the destination MN.

Meanwhile, information about BSS can be used as ESSs (extended servicesets). Referring to FIG. 5, a field <To BSS, From BSS> of a framecontrol field 510 according to an 802.11 header can be converted into afield <To ESS, From ESS> (511).

If the field <To ESS, From ESS> has a value of <0, 1>, a packet istransmitted from a wireless network to a wired network. If the field <ToESS, From ESS> has a value of <1, 0>, the packet is transmitted from awired network to a wireless network. If the field <To ESS, From ESS> hasa value of <0, 0>, the packet is transmitted within a wireless network.

FIG. 6 is a flowchart illustrating the transmission of data by a mobilenode according to an exemplary embodiment of the present invention.

When transmitting data, an MN needs to specify a destination device towhich the MN wishes to transmit the data. If the destination deviceexists outside a wireless network, the MN must designate a relay portalto relay the data to the destination device. Therefore, referring to themethod illustrated in FIG. 6, in operation S602, it is determinedwhether the MN has chosen or designated a relay portal. In operationS604, if the MN has not yet chosen or designated a relay portal, the MNchooses one of a plurality of portals in the wireless network as a relayportal. In detail, the MN chooses one of the portals which share thesame wired network and the same wireless network and are connected toboth the wired network and the wireless network as a relay portal. Inthe network environment illustrated in FIG. 4, two separate wirednetworks are connected to a wireless network, and thus, a total of 2relay portals can be designated. In operation S610, it is determinedwhether the MN has designated two or more relay portals. In operationS620, if two or more relay portals are designated, it is determinedwhether a destination MN 212 can be reached through any of the relayportals. Referring to FIG. 4, since the MN 212 is connected to the upperwired network 51, it can be reached through the mesh portals 113 and114, and thus, packets destined for the MN 212 are transmitted to themesh portals 113 and 114. Likewise, if the destination MN is determinedin operation S620 to be reachable through any of the relay portals, datais transmitted to the relay portal through which the destination MN isreachable in operation S628. Also, if there is no information aboutdetermination in operation S624, data is transmitted to all relayportals. If the MN has designated only one relay portal, data istransmitted to the relay portal in operation S612.

FIG. 7 is a flowchart illustrating the transmission and reception ofdata using a mesh portal according to an exemplary embodiment of thepresent invention.

Referring to the method illustrated in FIG. 7, a first device transmitsa packet to designate a predetermined portal as a relay portal. Inoperation S702, the predetermined portal receives from the first devicethe packet which indicates that the predetermined portal has beendesignated as a relay portal. In operation S704, the predeterminedportal generates an update packet in which an identifier of the firstdevice, for example, a MAC address of the first device, is set as asource address. In operation S706, the predetermined portal transmitsthe update packet to a wired network using a broadcast method. As aresult, portals or bridges connected to the wired network register adevice corresponding to the MAC address included in the update packet,i.e., the first device, with a filtering database. In operation S708,the predetermined portal receives a packet transmitted by the firstdevice. In operation S712, the predetermined portal transmits the packetto the wired network.

According to an exemplary embodiment of the present invention, it ispossible to prevent a loop from being generated using relay portals anda main portal.

An exemplary embodiment of the present invention enables data to betransmitted to and received from a wired network using a relay portal.

It will be apparent to those skilled in the art that variousmodifications and changes may be made thereto without departing from thescope and spirit of the invention. Therefore, it should be understoodthat the above exemplary embodiments are not restrictive butillustrative in all aspects. The scope of the present invention isdefined by the appended claims rather than the detailed description ofthe invention. All modifications and changes derived from the scope andspirit of the claims and equivalents thereof should be construed to beincluded in the scope of the present invention.

1. A frame comprising: an identifier of a receiving device which is toreceive data; an identifier of a sending device which transmits thedata; and an identifier of one of a plurality of portals in a wirelessnetwork to which the sending device is connected, the data prioritizedsuch that the data is transmitted to the connected portal.
 2. The frameof claim 1, further comprising a frame control field, wherein the framecontrol field comprises: information indicating whether the sendingdevice is connected to at least one of a first wireless network and afirst wired network; and information indicating whether the receivingdevice is connected to at least one of a second wireless network and asecond wired network.
 3. The frame of claim 1, wherein the frame istransmitted by a portal identified by a portal identifier if the frameis transmitted from the wireless network to a wired network.